Root Rot: Signs, Causes and How to Save Your Plant

By the Garden Voila editorial team · Updated October 30, 2026 · How we verify

Root rot is the decay of a plant’s roots, most often caused by soil that stays waterlogged, which starves roots of oxygen and allows water molds and fungi such as Pythium, Phytophthora, Rhizoctonia and Fusarium to invade. Signs include wilting even though the soil is wet, yellowing lower leaves, stunted growth, a sour or rotten smell from the soil, and brown or black, mushy roots that slough off when touched. To save a plant with root rot, remove it from its pot, wash and inspect the roots, cut away every soft, discolored root with clean scissors, repot into fresh, fast-draining potting mix in a clean pot with drainage holes, and water sparingly until new growth appears. Prevention comes down to drainage and watering only when plants need it.

Root rot at a glance: healthy vs rotten roots

What causes root rot?

Roots need oxygen as much as water. In soil that stays saturated, the air spaces fill with water and roots begin to suffocate and die. Weakened roots are then easily attacked by soil-borne water molds and fungi that thrive in wet conditions. The Wikipedia article on root rot explains that it is one of the most common causes of plant death, both indoors and in gardens with poor drainage. The University of Wisconsin Plant Disease Diagnostics Clinic article on root rots of houseplants notes that overwatering, poorly draining potting media and pots without drainage holes are the main contributing factors in houseplants.

• Overwatering: watering on a fixed schedule rather than when the soil is dry enough.
• Poor drainage: pots without holes, decorative pots holding water, heavy or old potting mix that has broken down, compacted or clay soils outdoors.
• Oversized pots: a lot of wet soil around a small root system stays wet for days.
• Cool temperatures and low light: plants use less water in winter, so soil stays wet longer.
• Contaminated soil, pots or tools carrying root rot pathogens.
• Fungus gnat larvae, which can spread root rot organisms between plants.

What are the signs of root rot?

• Wilting or drooping even though the soil is moist, because damaged roots cannot take up water.
• Yellow leaves, often starting with the lower, older leaves.
• Brown, crispy or black leaf edges and leaf drop.
• Stunted or no new growth.
• Soft, dark stem base, a sign the rot has spread to the crown (crown rot).
• Sour or rotten smell from the potting mix.
• Soil that stays wet for a week or more after watering.
• Mold, algae or fungus gnats on the soil surface.

Many of these symptoms look like underwatering, which causes confusion. Check the soil before watering more: if it is wet and the plant is wilting, suspect root rot. See overwatering vs underwatering for a side-by-side comparison, and try the overwatering checker.

How do you save a plant with root rot?

1. Remove the plant from its pot. Gently slide it out and shake or wash away the old soil so you can see the roots clearly.
2. Inspect the roots. Healthy roots are firm and light colored. Rotten roots are brown or black, mushy, and the outer layer slides off.
3. Cut away all rotten roots. Use clean, sharp scissors or pruners, wiped with 70 percent rubbing alcohol between cuts, and cut back to firm, healthy tissue. Be thorough; leaving rotten roots lets the rot continue.
4. Trim the top if many roots were lost. Removing some leaves reduces the water the plant needs while roots regrow.
5. Repot into fresh mix. Use new, fast-draining potting mix suited to the plant (add perlite or bark for most houseplants) and a clean pot with drainage holes, only slightly larger than the remaining root mass.
6. Water lightly. Water once to settle the mix, then wait until the top inch or two is dry before watering again. Keep the plant in bright, indirect light and out of cold drafts.
7. Be patient. New roots and leaves may take several weeks. Do not fertilize until you see new growth.

What if all the roots are rotten?

If no healthy roots remain, the plant may still be saved by taking cuttings. Many houseplants, including pothos, philodendron, tradescantia, coleus, begonias, snake plants, succulents and fiddle-leaf figs, root readily from stem or leaf cuttings. Cut healthy stems above the rotted area with clean tools, remove lower leaves, and root them in water or a moist, airy mix such as perlite. For succulents, let cuttings dry for a few days to form a callus before planting. Discard the rotted plant and its soil, and scrub the pot with hot, soapy water before reuse.

Should you use hydrogen peroxide or fungicide for root rot?

Some gardeners rinse trimmed roots in a dilute hydrogen peroxide solution (one part 3 percent hydrogen peroxide to two to four parts water) to reduce pathogens and add oxygen, or dust cut roots with cinnamon. Evidence for these home remedies is limited, and strong solutions can damage healthy roots. Fungicides labeled for root rot organisms are used in greenhouses but are rarely needed for houseplants if you remove all rotten tissue and correct watering. The key fix is always improving drainage and watering practices.

How do you prevent root rot in houseplants?

• Water by need, not schedule. Check the soil with a finger or moisture meter. Most houseplants want the top inch or two to dry before watering; succulents and cacti need the mix to dry almost completely.
• Use pots with drainage holes. If you love a decorative pot without holes, use it as a cachepot with a plastic nursery pot inside, and empty any water that collects.
• Empty saucers within 15 to 30 minutes of watering.
• Choose the right potting mix: airy, well-draining mixes with perlite, bark or pumice for most houseplants; gritty mixes for succulents; orchid bark for epiphytes.
• Size pots correctly: move up only one size (about 1 to 2 inches wider) at a time.
• Repot every one to two years, since old potting mix breaks down and drains poorly.
• Water less in winter when plants grow slowly and light is low.
• Improve light and air flow so soil dries evenly.

Root rot in garden plants and trees

The Iowa State University Extension article on root rots of houseplants stresses that prevention through proper watering and well-drained media is far more effective than any treatment after rot sets in, and the same principle applies outdoors.

Outdoors, root rot affects plants in poorly drained or compacted soils, low spots where water collects, and areas that are overwatered by irrigation. Raspberries, rhododendrons, azaleas, yews, boxwood, fruit trees such as cherries and apricots, and many vegetables are susceptible to Phytophthora root rot. Signs include gradual decline, small yellow leaves, branch dieback and, in trees, dark cankers at the base. Prevention is about site and drainage: plant in raised beds or on mounds in heavy soil, avoid overwatering, keep mulch away from trunks, and choose tolerant plants for wet sites. See best soil for fruit trees for testing and improving drainage, and the garden watering calculator to avoid overwatering beds.

Which plants are most prone to root rot?

Dealing with more than one problem? Our plant pests and diseases guide lists every insect and disease we cover, organized by symptom.

Root rot FAQ

How do you water to avoid root rot?

The most reliable habit is to check the soil before every watering rather than following a calendar. Push a finger into the potting mix to the second knuckle, or use a wooden skewer or moisture meter. If it feels damp, wait. When it is time to water, water thoroughly until water runs from the drainage holes, so the whole root ball is moistened and excess salts are flushed out, then let the pot drain completely and empty the saucer. Lifting pots is another useful test: a freshly watered pot is noticeably heavier than one that needs water. In winter, when light is low and growth slows, most houseplants need water much less often, sometimes only every two to three weeks. Use the garden watering calculator for outdoor beds, where rain and soil type change how often to water.

Is it root rot or something else?

If you see tiny flies around the soil as well, see how to get rid of gnats in plants, since fungus gnats and root rot often appear together. For yellowing leaves with other causes, try the yellow leaf identifier.

Does root rot happen in hydroponics?

Yes. In hydroponic and water-culture systems, warm, poorly oxygenated nutrient solution encourages Pythium root rot, which turns roots brown and slimy. Keep the solution cool (ideally below about 72°F), aerate it with an air stone, change it regularly and keep reservoirs clean and dark. See our hydroponic garden guide for setup basics.

Can root rot be caused by too little light?

Indirectly, yes. Plants in low light grow slowly and use far less water, so the same watering routine that suits a plant in a bright window can leave a plant in a dim corner sitting in wet soil for days. If you move a plant to lower light or into winter conditions, water it less often. Improving light, with a brighter window or a grow light, helps plants use water and recover after root rot treatment.

With good drainage, the right potting mix and watering only when plants need it, root rot is almost entirely preventable, and most plants caught early make a full recovery.

Sources: University of Wisconsin Plant Disease Diagnostics Clinic, Root Rots on Houseplants; Iowa State University Extension, Root Rots of Houseplants; Wikipedia, Root rot.

Checking the roots and deciding whether to save the plant

The University of Wisconsin’s root rots on houseplants page says affected plants wilt even though the soil is wet, grow slowly, and may show yellow or red leaves that mimic a nutrient deficiency. To confirm, slide the plant out and look at the roots: diseased roots are soft and brown and may smell bad. The usual causes are soil-borne fungi and water moulds, mainly Pythium, Phytophthora, Rhizoctonia solani and Fusarium, which prefer wet soil and whose spores survive for long periods in soil and plant debris.

• Decide honestly: discarding the plant is often the best and most cost-effective option. Chemical fungicides are not recommended for houseplants because few are available to home gardeners and they tend to be expensive.
• If you keep it: reduce soil moisture, water enough to prevent drought stress but avoid overwatering.
• Repot properly: use a pot with drainage holes, no rocks or gravel in the bottom (they impede drainage), and pasteurised commercial potting mix, not garden soil. Add peat moss or other organic material to heavy mixes.
• Prevent: buy from reputable sources, never reuse potting mix or drainage water, and disinfest tools, work surfaces and clay pots with a 10 percent bleach or detergent solution or alcohol. Throw out plastic pots that held infected plants.

Our garden watering calculator helps match watering to pot size, and the plant problem identifier helps confirm the cause.

Reviewed October 2026. Sources: University of Wisconsin Extension, Root Rots on Houseplants